Method and apparatus for treating leather



Dec. 8, 1970 o o 'H; ETAL 3,545,095

METHOD AND APPARATUS FOR TREATING LEATHER Filed Sept. 17, 1968 2 Sheets-Sheet 1 k III II III I llll 071/? f0 r. s Fl /Jo 4 a pa 5 56 w AV /{Mk0 ha/ Dec. 8, 1970- J. DOKOUPIL ETA!- METHOD AND APPARATUS FOR TREATING LEATHER Filed Sept. 17, 1968 2 Sheets-Sheet 2 United States Patent 3,545,095 METHOD AND APPARATUS FOR TREATING LEATHER Jii'i Dokoupil, Jii'i Zubik, and Jii-i Zdrahal, Krnov, Czechoslovakia, assignors, by mesne assignments, to Svit, narodni podnik, Gottwaldov, Czechoslovakia, a corporation of Czechoslovakia Filed Sept. 17, 1968, Ser. No. 760,235 Int. Cl. F26b 5/14 US. CI. 34-14 7 Claims ABSTRACT OF THE DISCLOSURE With a leather treating method and apparatus for drying and smoothing leather, the leather is continuously conveyed through vibratory and heating elements so that the treatment takes place in a single pass. During this treatment, vibratory elements provide the leather with the desired physical condition, and in addition through heating and the vibratory elements moisture is removed so that the leather is finally put from an initial relatively Wet condition into a relatively dry condition,

BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for treating leather.

From a theoretical point of view, the manufacture of leather includes chemical as well as mechanical treatments which take place on thet raw hides while they are converted into leather which has the required physical and chemical as well as esthetic qualities. The chemical and mechanical treatments which are performed on leather at the present time can be considered as so-called wet treatments and dry treatments, respectively. The wet treatments are for the most part characterized by physically and chemically treating hides, these methods being known as curing leather.

In an in-between state, between the wet and dry treatments, is the so-called pre-treatment. The purpose of the latter operation is to change wet leather, which is in a completely finished form from the practical chemical point of view, into a dry state. In the dry state, the leather undergoes certain physical and chemical efiects, known as curing and finishing leather, with the result that the finished leather has not only the required physical but also the required esthetical properties.

The general main object of the treatment of leather is to remove Water therefrom, so that the leather is changed from a Wet condition having from 50 to 80 percent water into a dry condition having from 12 to 20 percent water. There is also a general tendency to simultaneously achieve in this state the highest possible increase in the planar or surface area of the leather, as compared to the wet state thereof, which makes it possible to increase the surface area under the best conditions and to achieve a flexible leather which is completely fiat and prepared for further finishing operations, such as leather ironing, leather buffing and the like.

The transition of leather from the wet to the dry state is at the present time brought about by complex mechanical operations, the most typical of which involves a series of machines and operations including sammying, setting-out, drying, moistening, staking, and final drying.

The sammying operations press or ring water from the leather by mechanical pressing, which requires relatively little energy. Setting-out increases the surface area of the leather, while the leather is still in a wet condition, so as to make the leather fiat, to remove all wrinkles therefrom, and to smooth the grain side of the leather. Drying removes water, as a result of thermal elfects, by evapora- 3,545,095 Patented Dec. 8, 1970 tion during the drying operation, last changes take place in the body of the leather. The thermal effects, however, also result in unnecessary adhering of the leather fibers to each other, which brings about undesirable stiffening of the leather to such an extent that mechanical staking is essential.

As a result of staking operations, the leather fibers are again separated. In order to attain the required efliciency of the staking and to exclude at the same time possible damage to the leather it becomes necessary to include in the line of operations moistening (mulling) of the leather, which is carried out prior to staking. Following the staking operation, repeated drying is essential to attain the necessary humidity for the final treatment with the required stability.

All of the above indicated operations are carried out on separate machines in interrupted cycles. The sammying is done on rotary drying presses or in some cases on static package presses. Setting-out is performed on a roller setting-out table. Drying is primarily carried out by pasting the leather on glass tables and then passing a stream of air against the surface of the leather in a suitable drying tunnel.

Vacuum dryers have been used in recent times. In the case of such dryers, the leather is placed on a chromeplated table and heated under low pressure conditions, which results in the lowering of the evaporation temperature of water and in increasing the elfect of the drying process. Also, pasting of leather on tables and heating the leather with a stream of hot water has been used in some cases, this process being known as Secotherm. There are some situations in which leather is dried while being freely hung over wooden or metallic bars.

The main goal of all types of drying is to produce leather which is fiat and possesses no deformation particularly at the marginal areas, and which does not lose any of the surface area during the drying, while at the same time the drying time should be as short as possible and the drying should have a low consumption of power and steam.

Subsequent moistening is primarily carried out by passing the leather through water or by spraying water or steam on the leather. In some cases, the leather is covered with wet or moist sawdust. The following staking is done either on lever machines which now are not widely used, or on roller machines having spiral knives, which are not very efficient. Also, feed-types of stake machines are used which operate on the principle of vibratory elements. The final drying is carried out in bar-type drying chambers or in vacuum dryers.

Irrespective of which of the known methods and apparatus are used, they all suffer from the drawback of requiring interrupted cycles and separate operations on separate machines. The machines simply do such work as was previously performed manually, and the leather must be fed into and removed from the machines by operators. In addition to operators at the several machines, more operators are required to transport the leather from one machine to the next. Thus, the entire process is purely mechanical because the major part of the energy is derived from the machines, and there is practically no degree of automation.

In recent times there have been attempts to improve these conditions by providing through-put machines which attempt to process the leather during a single pass through a machine and thus eliminate the necessity of passing the leather through a given machine twice or in some cases even more times. There are known, for instance, throughput staking machines equipped with vibratory elements, and also through-put vacuum dryers.

A development of automated machines is exceedingly ditlicult primarily because of the irregular shape of leather which, in addition, becomes very soft when between the wet and dry state so that it acts like a flexible rug, is easily damaged, and the surface is easily provided with wrinkles, folds, creases, and the like. Under these conditions it becomes almost impossible to achieve any degree of automation with presently known principles and equipment.

In addition to the trend toward the use of through-put types of machines to replace individual machines there is a tendency from the chemical standpoint of tanners to reduce the manufacturing stages by dewatering the leather while at the same time excluding at least to some extent the possibility of the leather becoming stiff as result of the drying thereof. There are known processes wherein leather is dried in a frozen condition or water is replaced in the leather by another liquid, mostly an organic solvent, with a lower evaporation point and other physical properties to prevent leather from becoming stiff.

However, these latter methods are impractical, especially for mass production. Therefore, they have not yet been used by tanners and leather manufacturers. Among the most important drawbacks of these methods are the loss and gain of surface area.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a method and apparatus which will avoid the above named drawbacks.

An important object of the invention is to provide a single machine through which the leather passes to re ceive its entire treatment.

Another object of our present invention is a method according to which the leather is changed from a wet to a dry state and is at the same time given the required properties in a highly efiicient manner.

With the method and apparatus of the invention no leather is taken away. The entire treatment consists in removing water from the leather, bearing in mind that water has been soaked into the leather during the wet treatment. At the same time, the method and apparatus of the invention keeps the leather pliable while taking away water from the leather so that there is no loss of surface area. On the contrary, there is a gain of surface area so that the leather is prepared for further treatment in a flat and unwrinkled condition.

Thus, with the invention all of the known disadvantages are removed. The leather, according to the present invention, is continuously transported while held between a pair of conveyor belts which convey the leather in fiat condition and reliably prevent creasing or bending of the leather. By way of these conveyor belts which are preferably resilient and vapor-permeable known treatments are performed on the leather. Thus, a vibratory treatment is provided to remove water as a result of mechanical action, constituting sammying. During continued transportation of the leather between the conveyor belts an increase in the surface area is achieved, which is due to the expanding effects derived from vibratory elements. At the same time, wrinkles are removed from the leather and the leather becomes fiat and even, constituting setting-out operations.

Then, the leather is thermally treated while still retained between the conveyor belts. Heat is directed to the leather through the permeable conveyor belts. The heat can be derived from heat-exchange, convex or contact exchange, or from generation in the body of the leather by a highfrequency field derived from any source of current. The entire process can be speeded up by bringing about thermal treatment under conditions of low pressure in accordance with any known method which enables a lowering of the evaporation point of the water and a shortening of the thermal treatment stage with regard to the consumption of time and length of the thermal treatment itself. Vapor passes through the conveyor belts which are vapor-permeable or may be in the form of perforated sheets.

Thermally removing water to bring about drying has an influence on terminating the last chemical changes in the leather. The thermal treatment brings about adhering of the leather fibers to each other with the result of stiffening the leather and simultaneous shrinking and loss of surface area. For this latter reason the invention provides changing thermal effects by mechanical treatment, such as vibratory means. This is done with the aid of known devices and according to known methods for the purpose of defibrating the partially adhering fibers and to regain lost surface area. The change of thermal effects and the known results of vibratory elements may be applied freely but depend upon the properties of the raw hides and the required yields of planar or surface area, While requiring no more operators to carry out the operations, as the leather passes through the thermal and mechanical treatments in a single pass.

According to the invention, the leather is processed from a fully wet state containing 60-80 percent of water to a fully dry state containing 12-20 percent of water, without any loss of planar or surface area. The increase of area can be achieved by the mechanical effects of the vibratory elements at any stage of interruption of the thermal effects, with the resulting leather being in a fiat state free of wrinkles, folds or rolled or curled margins. Additional operations up to the finishing of the leather can take place directly after the method of the invention has been carried out.

As compared with known methods and apparatus, with the method and apparatus of the present invention individual leather pieces are treated continuously in a single machine rather than in separate machines. Individual feeding of leather into, and removal from, separate machines including dryers is eliminated so that labor costs are lowered and operators are no longer exposed to conditions of fatigue. Less floor space is required for the operation of the method and for the apparatus of the invention because only one machine is required. The influences of several different operators on the quality of the product are eliminated since the entire process is automated to achieve maximum quality while selecting optimum parameters of mechanical and thermal effects.

In the apparatus of the invention, the vibratory elements are those which are used in conventional throughfeed staking machines where stiff dry leather is stretched and staked by tools having rows of pegs meshing with one another, such apparatus being used with the method of the invention for stretching hot and Wet leather which has shrunk during the thermal drying cycle. However, with the invention there is no staking of stiff leather because the leather does not get stiff during the entire treatment in accordance with the invention.

In an example of treatment of leather according to the invention to achieve leather for use, for instance, at the side of a container, the leather is processed during its entire treatment between a pair of resilient fluid-permeable conveyor belts which are permeable to Water as well as air and which are resiliently pressed against each other to hold the leather therebetween. At first, dewatering is carried out by mechanical oscillatory pressure from an initial state where a 50-80 percent of water content is reduced to a 30-60 percent of water content, and then additional dewatering is achieved thermally by contact heating until the minimum of 5-10 percent is achieved with the temperature of the leather being 60-100" C. The leather is treated, alternately with the heating, mechanically by vibratory elements having projections which are vibrated at a frequency of 5-50 cycles per second. Thus, while in a heated condition, the leather is stretched to a minimum of 5-15 percent of its area, and thermal dewatering takes place by an additional 5-10 percent while the leather is again stretched by mechanical vibratory elements to an extent of 5-20 percent of its area. This alterhate thermal and mechanical treatment is applied until there remains only 12-20 percent of Water content in the leather.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. 1 is a schematic perspective illustration of an apparatus of the invention for carrying out the method of the invention; and

FIG. 2 is a schematic elevation of the manner in which the apparatus operates to carry out the method of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS A lower endless resilient fluid-permeable conveyor belt 2 cooperates with and, is generally situated beneath, an upper endless conveyor belt 3 made of the same material. These belts press against each other to compress between themselves leather 1 which is carried between the belts and through the machine. Both of the belts are first directed through a vibratory means 4 the lower part of which is driven from a drive 6. Water is mechanically released from the leather and is removed from the upper part of the vibratory means 4 by a discharge means 5 which sucks the water vapor out. The mechanical vibratory elements serve to mechanically remove water from the leather.

Then the belts with the leather therebetween are guided over a vertical system of flat heating bodies 7 forming a series of heating means, the bodies 7 having fiat upper surfaces engaging the belts. Inlet pipes 14, 15, 16 supply a heating medium, such as steam, into the hollow heating bodies with the latter being drained through an outlet pipe 13 (FIG. 2). The space around the entire system of flat heated bodies is closed by a wall 20, and a discharge system 17 is provided for exhausting vapor out of the enclosure defined by the wall 20.

Situated on one side of the vertical series of fiat heating bodies 7 is a vertical series of vibratory means 9, between which the belts are guided. As is apparent from FIGS, 1 and 2, guide rollers R are provided for alternately guiding the belts first across a heating body 7 and across the upper element of a pair of vibratory elements 9, 10, then in the opposite direction from said vibratory element across the next lower heating body, and so on back and forth alternately between the heating bodies and between the vibratory means to achieve alternate thermal and mechanical vibratory treatments until the leather is finally removed at the left end of the machine as viewed in FIGS. 1 and 2. The vibratory elements 9, 10 stretch the leather. The elements 9 are situated over the respective element 10, the elements 10 being driven from a drive 11.

The upper belt 3 is shorter than the lower belt 2 and is guided around rollers R along an upper path and around the rollers R While the lower conveyor belt 2 is longer and is guided in part around the same rollers R and then around rollers R along a bottom path. Both of the belts 2 and 3 of the conveyor are driven from a single drive 19. A control panel 18 is provided for controlling the opera tion and a regulator 12 adjusts the intensity of the vibration.

The apparatus of the invention operates as follows:

The operator will place a piece 1 of wet leather on the lower conveyor belt 2 where it extends to the right beyond the upper layer conveyor belt 3. Then, the leather is conveyed between the belts 2 and 3 through the vibratory means 4 where a great amount of water is mechanically removed by bending the leather between projections P of the vibratory means (clearly seen in FIG. 2). The leather is directed, while being held between the conveyor belts, across the upper fiat surface of the uppermost heating body 7 and is heated at this place to a relatively high temperature enabling additional water to be easily removed. As soon as the conveyors have moved the leather toward left beyond the uppermost heating body they are guided backwardly between the uppermost vibratory means 9, 10 where again projections bend and stretch the leather. Then, both of the conveyor belts together with the leather therebetween are directed to the second heating body 7 and enter a space 8 between the uppermost and the next lower heating body. Due to the fact that the leather has turned around an upper left guide roller R it is now the other side of the leather which contacts the surface of the second heating body 7, whereas at this time the first side of the leather is heated by radiation from the lower side of the upper heating body 7. Upon leaving a heating body 7 toward right, a guide roller R of a series of such rollers on the right-hand side of the heating bodies directs the belts again to the left to the next heating body. The alternate thermal and dynamic effects on the leather are carried out until 12-20 percent of moisture remains in the leather.

With different types of leather, different requirements may require either the thermal or the mechanical treatment to be extended. The structure can easily be varied accordingly. Individual vibratory elements can be put out of operation or the entire vibration system can be arranged on the opposite side or on both sides of the heating bodies. Also, several vertical series of heating and vibratory elements can be arranged next to each other.

While steam has proved to be most suitable for the heating medium of the fiat heating bodies, some of these bodies can be provided with a high frequency current for achieving heating of the leather dielectrically.

We claim:

1. A leather treating method for treating leather in a phase between a wet condition and a dry condition, comprising the steps of conveying the leather between a pair of endless conveyor belts formed of a fluid-permeable sheet material initially in a wet condition, containing from about 50 to percent of water, alternately through stages of mechanical vibratory elements operating said vibratory elements at or greater than 5 cycles per second, and heating elements, and continuing the movement of the leather through these stages until the water content of the leather is reduced down to from about 12 to 20 percent.

2. In a machine for treating leather, a pair of endless conveyor belts between which the leather is held while being treated, said belts being formed of a fluid-permeable sheet material permitting heat to be applied to the leather through said belts while moisture can move out from the leather through said belts, a series of vibration means, operating at or greater than 5 cycles per second, a series of heating means, and guide means coacting with said belts for guiding same in several passes alternately through said series of vibration means and said series of heating means in order to stretch the leather between said belts while simultaneously drying the leather.

3. The combination of claim 2 and wherein additional vibration means is provided between which said belts pass first to convey the leather therethrough for mechanically removing water from the leather.

4. The combination of claim 2 and wherein the vibration means of said series of vibration means are arranged one above the other while said series of heating means are in the form of a plurality of heating bodies also arranged one above the other, said series of vibration means being situated on at least one side of said plurality of heating bodies.

5. The combination of claim 4 and wherein said series of vibration means and said plurality of heating bodies are arranged one next to the other at a plurality of difierent elevations with said guide means for said belts guiding the latter from one to the next elevation to pass alter- References Cited nately in sequence through said series of vibration means and heating means. UNITED STATES PATENTS 6. The combination of claim 5 and wherein said plu- 1,741,755 12/1929 Chase IV et a1. 34-164X rality of heating bodies have upper smooth surfaces to 3,077,673 2/1963 Cohen et a1. 3418X engage the conveyor belts. a

7. The combination of claim 6 and wherein a high W IAM E- WAYNER, Primary Examiner frequency current source is operatively connected with said plurality of heating bodies for dielectrically heating the leather. 34-18, 164; 219-388 

